(rule ((:INTERN (reaction ?reaction ?reactants . ?products) :var ?def))
      (dolist (reactant ?reactants)
	(assert! `(reactant ,reactant ,?reaction)
		 `(:REACTANT-OF-REACTION ,?def)))
      (dolist (product ?products)
	(assert! `(product ,product ,?reaction)
		 `(:PRODUCT-OF-REACTION ,?def))))